For the first time a large, randomized trial indicates a drug is helpful against Covid-19. However, we shouldn't get too excited yet. Not only has the paper not yet passed peer review, it doesn't conclude remdesivir, the drug in question, directly saves lives. Nevertheless, remdesivir is reported to hasten patient recovery, which would reduce strain on overstretched health services. Meanwhile, there is disappointing news on some other drugs for which high hopes were once held.

Many drugs have been touted as effective against Covid-19, but the claims (some to be ignored) have relied on small, non-randomized or poorly conducted studies – often all three.

In this case, a respectable 1,063 randomized patients across 22 countries took part in the US National Institute of Allergy and Infectious Diseases (NIAID) study. Peer reviewers are still assessing whether it was well conducted in other ways, but a pre-print won the approval of NIAID director Dr Anthony Fauci in a press conference with President Trump.

Patients in the trial took an average of 11 days to recover when given remdesivir, compared to 15 given a placebo. There was also a lower mortality rate for those on remdesivir, at 8 percent compared to 11.6 percent, but the difference wasn't quite statistically significant.

Dr Fauci, who has been skeptical of other trials, expressed optimism about the implications for other treatments, saying, "What it has proven is that a drug can block this virus."

A previous trial of remdesivir was stopped before completion, because China now lacks enough new patients for a useful sample and 12 percent of those participating suffered serious side-effects. The inconclusive findings have been published in The Lancet. 

“Politely, a published manuscript in The Lancet has more credibility than a White House briefing,” Professor Ian Seppelt of the University of Sydney, who was not involved in either trial, said in a media round-up.  Other experts also said they will wait for more data.

Remdesivir is an anti-Ebola drug, and was found to save lives during the outbreak in the Democratic Republic of Congo last year. However, another drug tried in parallel proved even more effective and has been taken up as the Ebola-fighting standard. Not being in widespread use, remdesivir stocks are limited.

The fact a drug designed to fight Ebola has effects against Covid-19 may stoke conspiracy theories that the two diseases are connected, just as trials of anti-AIDS drugs fed the discredited belief SARS-CoV-2 was modified to include elements from HIV. The truth is many viruses have features in common, allowing drugs to be repurposed, and the process is much quicker than making a new one from scratch.

The news is not so good elsewhere. The journal Med has announced that neither HIV drugs Lopinavir/ritonavir nor influenza-fighter Arbidol provided clinical benefits against Covid-19. The drugs were chosen based on in vitro activity and a record of effectiveness against related coronaviruses,

Worldwide 1,100 clinical trials have been registered, more than 500 of them randomized, to test possible Covid-19 cures. Of these, five are of remdesivir and 24 of the Trump-promoted hydroxychloroquine, some of which have been canceled early because of side-effects.